JPH1160253A - Forming mold and forming method of meniscus lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming mold and a forming method for a meniscus lens capable of getting a desired form while minimizing the forming quantity of a glass preform. SOLUTION: A meniscus lens is formed by placing a glass preform 14 between a pair of forming molds consisting of an upper mold and a lower mold and hot-pressing the preform. The upper mold of the meniscus lens forming mold is provided with the 1st upper mold 21 to bring the convex face formed at the lower end into contact with the center of the glass preform 14 to form a concave face of the meniscus lens and the 2nd upper mold 22 to slidably guide the 1st upper mold 21 in the pressing direction and bring the lower face into contact with the outer circumference of the glass preform 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mold for molding a meniscus lens made of optical glass and a method for molding the same.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a conventional molding method of a meniscus lens by a glass molding method. In a conventional molding method of molding a meniscus lens made of optical glass by a glass molding method, first, a glass preform 4 made of optical glass is placed on a concave surface of a lower mold 1, and then the lower mold 1 and the upper mold 2 are formed into a cylindrical shape. (FIG. 3), and then heats and softens the glass preform 4 in an inert gas (nitrogen gas, etc.) atmosphere, and then press-molds to form a meniscus lens 4a made of optical glass. (FIG. 4).

Generally, in molding a meniscus lens by a glass molding method, one lens surface is concave and the other lens surface is convex, so that the difference between the concave curved surface R (R is a radius) and the convex curved surface R is obtained. Therefore, the molding amount (the deformation amount of the glass preform) is relatively large. When the concave curved surface R is small and the convex curved surface R is large, the molding amount is particularly large.

For this reason, in the conventional molding of the meniscus lens by the glass molding method, a sufficient pressure is applied to the central portion of the glass preform, especially when the concave curved surface R of the lens is small and the convex curved surface R is large. Sufficient pressure was not applied to the outer peripheral portion of the glass preform, particularly the peripheral edge portion, so that it was difficult to successfully form the outer peripheral portion of the convex surface of the lens. In order to solve such a problem, conventionally, the thickness of the glass preform is increased in advance, and the molding amount is increased in the outer peripheral portion of the glass preform where sufficient pressure is not applied, so that the circumference of the glass preform is increased. The method of forming the outer peripheral portion of the lens convex surface by using the extension in the direction has been adopted.

However, in this conventional molding method, it is necessary to use a glass preform having a large thickness.
There is a problem that a small and lightweight lens cannot be formed. Furthermore, the larger the deviation from the center of the glass preform and the larger the difference between the curved surfaces R when the concave curved surface R is small and the convex curved surface R is large, the amount of the outer peripheral portion of the glass preform to which sufficient pressure is not applied In some cases, the outer peripheral portion cannot be formed in a desired shape.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and therefore, a meniscus lens capable of obtaining a desired shape while minimizing a molding amount of a glass preform. An object of the present invention is to provide a molding die and a molding method.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a meniscus lens molding die in which a glass preform is sandwiched between a pair of upper and lower molds and heated and pressed to form a meniscus lens. A first upper mold that presses the convex surface formed at the lower end thereof to the central portion of the glass preform to form a concave surface of the meniscus lens; and guides the first upper mold slidably in the pressing direction, and has a lower surface thereof. And a second upper mold that presses the outer peripheral portion of the glass preform against the outer peripheral portion of the glass preform.

Further, the present invention provides a method for forming a meniscus lens, wherein a meniscus lens is formed by sandwiching a glass preform between a pair of upper and lower molds and heating and pressing the glass preform. A first upper mold that presses the formed convex surface to the center of the glass preform to form a concave surface of the meniscus lens; and guides the first upper mold so as to be slidable in the pressing direction, and lowers the lower surface of the glass preform. Preparing an upper mold comprising: a second upper mold pressed against an outer peripheral portion; a step of placing a glass preform on a concave surface of a lower mold forming a convex surface of the meniscus lens; Heating the glass preform placed on the substrate under an inert gas atmosphere; and pressing the convex surface of the first upper die against the center of the heated glass preform. It is characterized by having; that simultaneously with step is pressed against the lower surface of the second upper die to the outer peripheral portion of the glass preform.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated embodiments. FIG. 1 shows a state before press molding using a mold of an optical glass meniscus lens to which the present invention is applied, and FIG. 2 shows a state after press molding using the same mold. .

The molding die of this embodiment has a pair of a lower die 11 forming the convex side of the meniscus lens and an upper die 20 forming the concave side of the meniscus lens.
A cylindrical body mold 13 is fitted to the peripheral surface 11b of the, and an upper mold 20 is fitted to the upper part of the cylindrical body mold 13.

The upper die 20 includes an outer upper die (second upper die) 22 slidably fitted on the inner peripheral surface of the body die 13 and a sliding member with respect to the outer upper die (second upper die) 22. It consists of a pair with an inner upper mold (first upper mold) 21 that fits as possible. Outer upper mold 2
2, a guide opening 22a having a circular section is formed at the center thereof and extends in the pressing direction (the vertical direction in FIGS. 1 and 2).
At the upper end, a flange portion 22 having a diameter larger than the inner diameter of the body mold 13 is provided.
c is formed. The inner upper die (first upper die) 21 includes
A columnar pressing portion (columnar portion) 21a slidably fitted in the guide opening 22a and a large-diameter disk portion (diameter expanding portion) 21b integrally fixed to an upper end of the columnar pressing portion 21a are formed. I have. At the lower end of the columnar pressing portion 21a, that is, at the lower end of the inner upper mold 21, a convex surface 21c for pressing the glass preform 14 made of optical glass to form the concave surface of the meniscus lens 14a is formed.

A lower surface of the outer upper mold 22 is provided with a guide opening 22a.
Is formed as a pressing surface 22b that is inclined in a direction approaching toward the concave surface 11a as the distance from the outer surface to the outside increases. When the outer upper mold 22 is attached to the body mold 13, the pressing surface 22 b abuts on the upper peripheral edge 14 e of the glass preform 14 placed on the concave surface 11 a of the lower mold 11. Upper peripheral edge 14e
Is pressed into contact with the upper outer peripheral portion including. The outer upper mold 22 is the body mold 1
3 is mounted such that the pressing surface 22b comes into contact with the upper peripheral edge 14e of the glass preform 14 placed on the lower mold 11, so that the mounting operation positions the glass preform 14 at the center on the concave surface 11a. That is, centering of the glass preform 14 is performed.
After attaching the outer upper die 22 to the body die 13 in this manner, the columnar pressing portion 21a of the inner upper die 21 is fitted into the guide opening 22a of the outer upper die 22.

The closest position of the outer upper mold 22 to the lower mold 11, that is, the closest position of the pressing surface 22 b to the concave surface 11 a of the lower mold 11 is determined by the height of the body mold 13. That is, the lower end of the body die 13 contacts the upper surface of the flange 11c formed on the outer periphery of the lower end of the lower die 11, and at the same time, the body die 13
Is determined by contacting the upper end of the flange 22c with the flange portion 22c.

The lowermost position of the inner upper die 21 with respect to the outer upper die 22, that is, from the lower end of the guide opening 22a to the convex surface 21c.
Is determined by the thickness of the spacer 23 disposed between the disk portion 21b and the upper surface of the outer upper die 22. The spacer 23 adjusts the thickness of the meniscus lens 14a formed from the glass preform 14,
In addition, it serves to apply pressure to the outer upper mold 22 by its own weight at the time of press molding. To adjust the thickness of the meniscus lens 14a, a spacer 23 having an appropriate thickness is appropriately selected and used.

In the press forming using the forming die having the above-described configuration, first, the body die 13 is set on the lower die 11 and the lower die 1 is set.
The glass preform 14 is placed on the first concave surface 11 a, and then the outer upper mold 22 is set on the body mold 13. In this setting, the glass preform 14 is centered as described above. Subsequently, the columnar pressing portion 21 is inserted into the guide opening 22a.
a, and the inner upper mold 21 is set.
A spacer 23 is disposed between the upper mold 1b and the upper surface of the outer upper mold 22. At this time, a gap having a predetermined width is opened between the disk portion 21b and the upper surface of the outer upper die 22. Thereafter, the entire mold is heated in an inert gas (nitrogen gas or the like) atmosphere to a temperature at which the glass preform 14 is softened to soften the glass preform 14, and then a pressure is applied to the disk portion 21b toward the lower mold 11. To form a meniscus lens 4a (FIG. 2).

In the first stage of pressing the softened glass preform 14, a convex surface 21c at the lower end of the columnar pressing portion 21a is used.
Is pressed against the glass preform 14 and concentrated on the central portion of the glass preform 14, whereby the lens is formed from the central portions of the concave and convex surfaces of the lens. When pressure is further applied to the disk portion 21b, the disk portion 21b comes into contact with and presses against the spacer 23. Then
The pressing surface 22b and the concave surface 11 of the lower mold 11 are provided on the outer peripheral portion of the glass preform 14 where pressure is not applied by the convex surface 21c.
a is applied to the glass preform 1
Pressure is applied uniformly from the central part to the outer peripheral part of 4.

As described above, according to the mold of the above embodiment to which the present invention is applied, even if the concave curved surface R of the lens is small and the convex curved surface R is large, the action of the pressing surface 22b is particularly effective. As a result, a sufficient pressure can be applied to the outer peripheral portion of the glass preform, so that the convex surface of the meniscus lens can be successfully molded to the outer peripheral portion while minimizing the molding amount of the glass preform.
Therefore, it is possible to form a meniscus lens even if a glass preform having a small thickness is used,
Therefore, a small and lightweight glass meniscus lens can be formed.

[0018]

As described above, according to the meniscus lens molding die and the molding method of the present invention, the upper mold is pressed with the downward convex portion formed at the lower end thereof against the glass preform to reduce the concave surface of the meniscus lens. A first upper mold to be molded, fitted on a peripheral surface of the first upper mold, guided slidably in the pressing direction with respect to the first upper mold, and having a lower end portion thereof at a peripheral edge of the glass preform; Since it is configured to include the second upper mold to be pressed, it is possible to obtain a desired shape while minimizing the molding amount of the glass preform, and it is also possible to obtain a meniscus even when using a glass preform whose thickness is not so large. Since the lens can be molded well, a small and lightweight lens can be molded.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state before press molding of a molding die to which the present invention is applied.

FIG. 2 is a cross-sectional view showing a state after press molding of the mold shown in FIG.

FIG. 3 is a cross-sectional view showing a state before press molding of a conventional molding die.

FIG. 4 is a cross-sectional view showing a state after press molding of the molding die shown in FIG. 3;

[Explanation of symbols]

 Reference Signs List 11 lower mold 13 trunk mold 14 glass preform 20 upper mold 21 inner upper mold (first upper mold) 22 outer upper mold (second upper mold) 23 spacer

Claims (6)

[Claims] 1. A meniscus lens forming mold in which a glass preform is sandwiched between a pair of upper and lower molds and heated and pressed to form a meniscus lens. A first upper mold that presses the formed convex surface to the central portion of the glass preform to form a concave surface of the meniscus lens; and guides the first upper mold so as to be slidable in the pressing direction, and lowers the lower surface of the glass preform. A second upper mold that is pressed against the outer periphery of the meniscus lens. 2. The molding die for a meniscus lens according to claim 1, wherein the second upper die has a guide opening penetrating in the pressing direction, and the first upper die is the first upper die. A mold for a meniscus lens, wherein a columnar portion provided with the convex surface at the lower end thereof is slidably fitted in the guide opening. 3. The meniscus lens mold according to claim 1, wherein the meniscus lens is fitted on each of the peripheral surfaces of the second upper mold and the lower mold, and the second upper mold has a lower end with respect to the lower mold. A mold for forming a meniscus lens, comprising: a body mold that defines an approach position and guides movement of a second upper mold with respect to a lower mold; and a spacer that defines a lowermost position of the first upper mold with respect to the second upper mold. 4. The meniscus lens molding die according to claim 3, wherein the first upper die has an enlarged diameter portion facing the upper surface of the second upper die, and the spacer is provided on the first upper die. A molding die for a meniscus lens disposed between the enlarged diameter portion of the die and the upper surface of the second upper die. 5. The meniscus lens mold according to claim 1, wherein the lower surface of the second upper mold pressed against the outer peripheral portion of the glass preform is in contact with the concave surface of the lower mold. A meniscus lens mold that centers the glass preform by sandwiching the glass preform. 6. A method for forming a meniscus lens, wherein a glass preform is sandwiched between a pair of upper and lower molds and heated and pressed to form a meniscus lens. A first upper mold that is pressed against the center of the glass preform to form a concave surface of the meniscus lens; and the first upper mold is slidably guided in the pressing direction, and the lower surface of the first upper mold is placed on the outer periphery of the glass preform. Preparing an upper mold comprising: a second upper mold to be pressed against; a step of placing a glass preform on a concave surface of a lower mold forming a convex surface of the meniscus lens; and placing the glass preform on a concave surface of the lower mold. Heating the heated glass preform in an inert gas atmosphere; and pressing the convex surface of the first upper mold against the center of the heated glass preform. Molding method of the meniscus lens and having a; a step is pressed against the lower surface of the second upper die to the outer peripheral portion of the glass preform.